import java.io.FileWriter;
import java.io.PrintWriter;
public class Main {
public static void main(String[] args) throws Exception {
String filename = "fileName.txt";
String[] linesToWrite = new String[] { "a", "b" };
boolean appendToFile = true;
PrintWriter pw = null;
if (appendToFile) {
pw = new PrintWriter(new FileWriter(filename, true));
} else {
pw = new PrintWriter(new FileWriter(filename));
// pw = new PrintWriter(new FileWriter(filename, false));
}
for (int i = 0; i < linesToWrite.length; i++) {
pw.println(linesToWrite[i]);
}
pw.flush();
pw.close();
}
}